1.1 Cybersecurity

conspicuously impact upon the performance of Smart Grid. Among all the factors, online monitoring and reacting have great capabilities in improving reliability which can be provided by WSANs in every part of Smart Grid assemblage, from

Due to WSANs' low costs, they can specifically affect the distributed generation and the production of renewable energy in generation part. Moreover, posts, overhead, and underground transmission lines are better to be online monitored through WSANs in transmission and distribution part. Eventually, WSANs can be employed in consumption part for substation and residential distribution networks, especially smart meters (AMI) [9] which are shown in Figure 1. Although WSANs provide numerous advantages, they encounter some challenges in issues such as real-time data delivery and high-rate data generation, since they have not been

As often as not, WSAN applications utilize IEEE802.15.4 which take advantage

Impulsive and robust noises of a power system environment and IEEE802.15.4 standard's intrinsic challenges force us to provide a minimum quality of service

The delay and reliability of WSAN are two prominent parameters in Smart Grid. In order to reach a required QoS level through optimizing network parameters, an elaborate analytical model is essential which is substantially similar to the reality. Table 1 depicts a summary of the most important applications in Smart Grid and their QoS levels in terms of data rate, latency, and reliability [2, 12]. As the table shows, in contrast to the reliabilities, the range of delays are relatively high.

of a low-power link leading to a low data rate transmission (250 kb/s) [10].

Reliability Latency Bandwidth (Kbps) Application –99.99% 2–15 s 10–100 AMIa –99.99% 500 ms–several min 14–100 Demand response –99.99% 20 ms–15 s 9.6–56 Distribution energy

99–99.99% 2–15 s 10–100 AMI

99–99.999% 100 ms–2 s 9.6–100 Distribution grid management 99–99.99% 2 sec–5 min 9.6–56, 100 is a good target Electric Transportation

Resources and storage

Demand response

(QoS) level to control and monitor applications of Smart Grid [11].

generation to consumption [7, 8].

Research Trends and Challenges in Smart Grids

specifically designed for Smart Grid.

Smart grid ecosystem monitoring and controlling via WSAN.

Figure 1.

a

76

Table 1.

Advanced metering infrastructure.

Communication requirements of smart grid technologies.

As stated by the Electric Power Research Institute (EPRI), one of the most challenges facing Smart Grid deployment is related to cyber security, and due to the increasing potential of cyberattacks and incidents against this critical sector, it becomes more and more interconnected. A large part of research of many organizations working on the development of Smart Grid such as NIST, NERC-CIP, ISA, IEEE 1402, and NIPP are devoted to security programs. In this paper we suggested a well-known standard, IEEE802.15.4, which the wireless link will be secured in different layers. For example, regarding secure communications, the MAC sublayer offers facilities which can be harnessed by upper layers to achieve the desired level of security. Higher-layer processes may specify keys to perform symmetric cryptography to protect the payload and restrict it to nodes or just a point-to-point link; these nodes can be specified in access control lists. Furthermore, MAC computes freshness checks between successive receptions to ensure that presumably old frames, or data which is no longer considered valid, do not transcend to higher layers. In addition, there is another insecure MAC mode, which allows access control lists merely as a means to decide on the acceptance of frames according to their (presumed) source.

The rest of the paper is organized as follows. In Section 2, we summarize related work. Section 3 lists the main contributions of the paper and their relation with literature. In this section we proposed an extended Markov. Reliability is analyzed accurately in Section 4. In addition, an accurate analysis of packet service time and end-to-end delay is investigated in Section 5. Numerical

and simulation results are presented in Section 6. In this section we validate our analysis by experimental results and Monte Carlo simulations. Finally, Section 7 concludes the paper.

3. The analytical model

DOI: http://dx.doi.org/10.5772/intechopen.84288

tions as well as Smart Grids.

use in our equations and diagrams.

standard for enthusiastic readers is in [36–38].

Symbol Definition bi,j,k State probability

m0 MacMinBE

m MacMaxCSMABackoffs

n MacMaxFrameRetries

τ Probability of starting CCA1 Lp Length of data packet

Pc Probability of collision

ρ Applied load to the queue

Table 2.

79

Summary of notations.

Ls Duration of successful transmission

Lack Duration of acknowledgment packet Lw,ack Acknowledgment waiting time

λ Packet arrival rate at the MAC sublayer

TService Average service time for uplink data block Tbackoff,i Average service time for backoff stage TCCA,i Average service time of carrier sensing W Packet waiting time in the queue W0 The mean remaining service time Q Number of packet in the queue

Lc Duration of failure transmission due to collision

Lm,ack Acknowledgment maximum waiting time (ACK time out)

In this section, an accurate analytical model is proposed for industrial applica-

In order not to get involved in useless elaborate calculations, we consider a star topology with a PAN coordinator, N nodes, and the slotted beacon-enabled CSMA/ CA mechanism. Acknowledgment is enabled, and a MAC sublayer buffer has also been designed. The input traffic can be saturated, but its distribution is deterministic. We also assume that the arrival rates for all nodes are the same, and nodes start sensing the medium independently. Table 2 shows the summary of notations we

Wi Maximum number of random backoffs in stage i

α Probability that channel is busy in CCA1 β Probability that channel is busy in CCA2

IEEE802.15.4 specifies physical and MAC layers, a low-rate and low-energy consumption solution [10]. This standard provides two channel access types: slotted CSMA/CA and unslotted CSMA/CA [34, 35]. Further information concerning the

A Reliable Communication Model Based on IEEE802.15.4 for WSANs in Smart Grids
